Power splitter with signal amplification

ABSTRACT

A power splitter that amplifies an input radio-frequency (RF) signal. The power splitter uses a single transistor in a common emitter stage of a cascode amplifier and two or more common base stages of the cascode amplifier to amplify and to split the input RF signal. A common base biasing signal can be used to simultaneously enable two or more of the common base stages to generate two or more amplified RF output signals.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a division of U.S. application Ser. No. 16/221,486filed Dec. 15, 2018, entitled POWER SPLITTER WITH CASCODE STAGESELECTION, which is a continuation of U.S. application Ser. No.15/042,334 filed Feb. 12, 2016, entitled POWER AMPLIFIER WITH CASCODESWITCHING OR SPLITTING FUNCTIONALITY (now U.S. Pat. No. 10,187,023issued Jan. 22, 2019), which claims priority to U.S. ProvisionalApplication No. 62/116,494 filed Feb. 15, 2015, entitled MULTIBAND POWERAMPLIFIER WITH CASCODE SWITCHING, the disclosure of each of which ishereby expressly incorporated by reference herein in its entirety forall purposes.

BACKGROUND Field

The present disclosure generally relates to power amplifiers.

Description of the Related Art

Some multiband power amplification systems use a common RF gain pathwhich is then switched (via a band switch) into one of a number ofmultiple filter networks or split (via a passive splitter) into aplurality of filter networks to support the various target frequencybands. The band switch is often implemented using SOI(silicon-on-insulator) or PHEMT (psuedomorphic high-electron-mobilitytransistor) technology which requires an additional semiconductor die tosupport the function, adding size and cost to the system. The passivesplitter is often implemented using passive lumped or distributedcomponents, also adding size and cost to the system. The band switch orpassive splitter also introduces loss into the system that degradesefficiency and requires increased current drain in the poweramplification system.

SUMMARY

In accordance with some implementations, the present disclosure relatesto a power amplification system. The power amplification system includesa first transistor having a base configured to receive an inputradio-frequency (RF) signal and having an emitter coupled to a groundpotential. The power amplification system includes a plurality of secondtransistors. Each one of the plurality of second transistors has arespective emitter coupled to a collector of the first transistor and isconfigured to, when biased at a respective base, output an output RFsignal at a respective collector. The power amplification system furtherincludes a biasing circuit configured to bias one or more of theplurality of second transistors based on a control signal.

In some embodiments, the biasing circuit can be further configured tobias the first transistor.

In some embodiments, the biasing circuit can include at least one of acurrent source or a voltage source configured to provide a biasingsignal that is routed to the one or more of the plurality of secondtransistors. In some embodiments, the biasing circuit can include acommon base biasing component configured to route the biasing signalbased on the control signal.

In some embodiments, the biasing circuit can include a plurality ofcurrent sources or voltage sources configured to provide respectivebiasing signals to the one or more of the plurality of secondtransistors. In some embodiments, the biasing circuit can include aplurality of common base biasing components configured to, when enabled,pass the respective biasing signals to the one or more of the pluralityof second transistors. In some embodiments, the biasing circuit caninclude a controller configured to enable one or more of the common basebiasing components based on the control signal.

In some embodiments, the power amplification system can further includean input matching component coupled to the base of the first transistorand configured to match the input RF signal. In some embodiments, thepower amplification system can further include a plurality of outputmatching components. Each one of the plurality of output matchingcomponents can be coupled to the respective collector of a respectiveone of the plurality of second transistors. In some embodiments, eachone of the plurality of output matching circuits can be configured tofilter the output RF signal to a respective frequency band.

In some embodiments, each one of the respective collectors of theplurality of second transistors can be coupled to a supply voltage via arespective inductor. In some embodiments, each one of the respectivecollectors of the plurality of second transistors can be coupled to anantenna switch. In some embodiments, each one of the respectivecollectors of the plurality of second transistors can be coupled to theantenna switch without an intervening band switch. In some embodiments,the antenna switch can include a combiner.

In some embodiments, the control signal can be a band select signal(BSS).

In some implementations, the present disclosure relates to aradio-frequency (RF) module including a packaging substrate configuredto receive a plurality of components. The RF module includes a poweramplification system implemented on the packaging substrate. The poweramplification system includes a first transistor having a baseconfigured to receive an input radio-frequency (RF) signal and having anemitter coupled to a ground potential. The power amplification systemincludes a plurality of second transistors. Each one of the plurality ofsecond transistors has a respective emitter coupled to a collector ofthe first transistor and is configured to, when biased at a respectivebase, output an output RF signal at a respective collector. The poweramplification system further includes a biasing circuit configured tobias one or more of the plurality of second transistors based on acontrol signal.

In some embodiments, the RF module can be a front-end module (FEM).

In some embodiments, the biasing circuit can include at least one of acurrent source or a voltage source configured to provide a biasingsignal that is routed to the one or more of the plurality of secondtransistors.

In some embodiments, the biasing circuit can include a plurality ofcurrent sources or current sources configured to provide respectivebiasing signals to the one or more of the plurality of secondtransistors.

In some implementations, the present disclosure relates to a wirelessdevice including a transceiver configured to generate an inputradio-frequency (RF) signal. The wireless device includes a front-endmodule (FEM) in communication with the transceiver. The FEM includes apackaging substrate configured to receive a plurality of components. TheFEM further includes a power amplification system implemented on thepackaging substrate. The power amplification system includes a firsttransistor having a base configured to receive the input radio-frequency(RF) signal and having an emitter coupled to a ground potential. Thepower amplification system includes a plurality of second transistors.Each one of the plurality of second transistors has a respective emittercoupled to a collector of the first transistor and is configured to,when biased at a respective base, output an output RF signal at arespective collector. The power amplification system further includes abiasing circuit configured to bias one or more of the plurality ofsecond transistors based on a control signal. The wireless devicefurther includes an antenna in communication with the FEM. The antennais configured to transmit the output RF signal.

For purposes of summarizing the disclosure, certain aspects, advantagesand novel features of the inventions have been described herein. It isto be understood that not necessarily all such advantages may beachieved in accordance with any particular embodiment of the invention.Thus, the invention may be embodied or carried out in a manner thatachieves or optimizes one advantage or group of advantages as taughtherein without necessarily achieving other advantages as may be taughtor suggested herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example wireless system or architecture.

FIG. 2 shows that, in some implementations, an amplification system caninclude a radio-frequency (RF) amplifier assembly having one or morepower amplifiers.

FIGS. 3A-3E show non-limiting examples of power amplifiers.

FIG. 4 shows that, in some implementations, an amplification system canbe implemented as a high-voltage (HV) power amplification system.

FIG. 5 shows that in some embodiments, a power amplification system caninclude a band switch.

FIG. 6 shows that in some embodiments, a power amplification system caninclude a cascode configuration with multiple common base cascodestages.

FIG. 7 shows that in some embodiments, a power amplification can includea single common base biasing component with band select logic.

FIG. 8 shows that in some embodiments, a power splitter can include acascode power amplifier with multiple common base stages.

FIG. 9 shows a flowchart representation of a method of amplifying an RFsignal.

FIG. 10 depicts a module having one or more features as describedherein.

FIG. 11 depicts a wireless device having one or more features describedherein.

DETAILED DESCRIPTION OF SOME EMBODIMENTS

The headings provided herein, if any, are for convenience only and donot necessarily affect the scope or meaning of the claimed invention.

Described herein are circuits, systems, and methods for amplifying an RFsignal having one of a plurality of frequency bands. In variousimplementations, a power amplification system includes a cascode poweramplifier as the gain stage and switches multiple common base cascodegain stages to accomplish the multi-band architecture. Such a poweramplification system offers advantage of sharing a common RF gain pathwithout adding the loss of a band switch. Band selection is alsoaccomplished without added additional process technology complexity oradditional die.

Referring to FIG. 1, one or more features of the present disclosuregenerally relate to a wireless system or architecture 50 having anamplification system 52. In some embodiments, the amplification system52 can be implemented as one or more devices, and such device(s) can beutilized in the wireless system/architecture 50. In some embodiments,the wireless system/architecture 50 can be implemented in, for example,a portable wireless device. Examples of such a wireless device aredescribed herein.

FIG. 2 shows that the amplification system 52 of FIG. 1 typicallyincludes a radio-frequency (RF) amplifier assembly 54 having one or morepower amplifiers (PAs). In the example of FIG. 2, three PAs 60 a-60 care depicted as forming the RF amplifier assembly 54. It will beunderstood that other numbers of PA(s) can also be implemented. It willalso be understood that one or more features of the present disclosurecan also be implemented in RF amplifier assemblies having other types ofRF amplifiers.

In some embodiments, the RF amplifier assembly 54 can be implemented onone or more semiconductor die, and such die can be included in apackaged module such as a power amplifier module (PAM) or a front-endmodule (FEM). Such a packaged module is typically mounted on a circuitboard associated with, for example, a portable wireless device.

The PAs (e.g., 60 a-60 c) in the amplification system 52 are typicallybiased by a bias system 56. Further, supply voltages for the PAs aretypically provided by a supply system 58. In some embodiments, either orboth of the bias system 56 and the supply system 58 can be included inthe foregoing packaged module having the RF amplifier assembly 54.

In some embodiments, the amplification system 52 can include a matchingnetwork 62. Such a matching network can be configured to provide inputmatching and/or output matching functionalities for the RF amplifierassembly 54.

For the purpose of description, it will be understood that each PA (60)of FIG. 2 can be implemented in a number of ways. FIGS. 3A-3E shownon-limiting examples of how such a PA can be configured. FIG. 3A showsan example PA having an amplifying transistor 64, where an input RFsignal (RF_in) is provided to a base of the transistor 64, and anamplified RF signal (RF_out) is output through a collector of thetransistor 64.

FIG. 3B shows an example PA having a plurality of amplifying transistors(e.g., 64 a, 64 b) arranged in stages. An input RF signal (RF_in) isprovided to a base of the first transistor 64 a, and an amplified RFsignal from the first transistor 64 a is output through its collector.The amplified RF signal from the first transistor 64 a is provided to abase of the second transistor 64 b, and an amplified RF signal from thesecond transistor 64 b is output through its collector to thereby yieldan output RF signal (RF_out) of the PA.

In some embodiments, the foregoing example PA configuration of FIG. 3Bcan be depicted as two or more stages as shown in FIG. 3C. The firststage 64 a can be configured as, for example, a driver stage; and thesecond stage 64 b can be configured as, for example, an output stage.

FIG. 3D shows that in some embodiments, a PA can be configured as aDoherty PA. Such a Doherty PA can include amplifying transistors 64 a,64 b configured to provide carrier amplification and peakingamplification of an input RF signal (RF_in) to yield an amplified outputRF signal (RF_out). The input RF signal can be split into the carrierportion and the peaking portion by a splitter. The amplified carrier andpeaking signals can be combined to yield the output RF signal by acombiner.

FIG. 3E shows that in some embodiments, a PA can be implemented in acascode configuration. An input RF signal (RF_in) can be provided to abase of the first amplifying transistor 64 a operated as a commonemitter device. The output of the first amplifying transistor 64 a canbe provided through its collector and be provided to an emitter of thesecond amplifying transistor 64 b operated as a common base device. Theoutput of the second amplifying transistor 64 b can be provided throughits collector so as to yield an amplified output RF signal (RF_out) ofthe PA.

In the various examples of FIGS. 3A-3E, the amplifying transistors aredescribed as bipolar junction transistors (BJTs) such as heterojunctionbipolar transistors (HBTs). It will be understood that one or morefeatures of the present disclosure can also be implemented in or withother types of transistors such as field-effect transistors (FETs).

FIG. 4 shows that in some embodiments, the amplification system 52 ofFIG. 2 can be implemented as a high-voltage (HV) power amplificationsystem 100. Such a system can include an HV power amplifier assembly 54configured to include HV amplification operation of some or all of thePAs (e.g., 60 a-60 c). As described herein, such PAs can be biased by abias system 56. In some embodiments, the foregoing HV amplificationoperation can be facilitated by an HV supply system 58. In someembodiments, an interface system 72 can be implemented to provideinterface functionalities between the HV power amplifier assembly 54 andeither or both of the bias system 56 and the HV supply system 58.

FIG. 5 shows that in some embodiments, a power amplification system 500can include a band switch 571. The power amplification system 500includes cascode power amplifier including a common emitter stage and acommon base stage. The common emitter stage includes a first transistor552 having an emitter coupled to a ground potential. The common basestage includes a second transistor 551 having a base coupled, via acapacitor 543, to the ground potential. The first transistor 552includes a base coupled, via a capacitor 545 and an input matchingcomponent 530, to an RF input for receiving an input RF signal. Thefirst transistor 552 also has a collector coupled to an emitter of thesecond transistor 551.

The second transistor 551 has a collector coupled, via an inductor 541,to a supply voltage (Vcc). The collector of the second transistor 551 isalso coupled, via a band switch 571, one or more output matchingcomponents 560 a-560 c, and an antenna switch 572, to an antenna 580 fortransmitting an output RF signal.

The power amplification system 500 includes a biasing circuit forbiasing the first transistor 552 and the second transistor 551. Thebiasing circuit includes a common emitter biasing component 520 that iscoupled to the base of the first transistor 552 via an RC decouplingcomponent. The RC decoupling component includes a resistor 544 coupledbetween the common emitter biasing component 520 and the base of thefirst transistor 552 and further includes a capacitor 545 coupledbetween the RF input and the base of the first transistor 552.

The biasing circuit further includes a common base biasing component 510coupled to the base of the second transistor 551 via an RC decouplingcomponent. The RC decoupling component includes a resistor 542 coupledbetween the common base biasing component 510 and the base of the secondtransistor 551 and further includes a capacitor 543 coupled between theground potential and the base of the second transistor 551.

The common emitter biasing component 520 is configured to, when enabled,receive a current from a current source 522 powered a battery voltage(Vbatt) and provide a biasing signal to the first transistor 552. Thebiasing signal may be a biasing current (e.g., the current generated bythe current source) or a biasing voltage. Similarly, the common basebiasing component 510 is configured to, when enabled, receive a currentfrom a current source 512 powered by the battery voltage and provide abiasing signal to the second transistor 551.

The power amplification system 500 is configured to receive an input RFsignal via the RF input and provide, as an output RF signal, anamplified version of the input RF signal via the antenna. Typically, theinput RF signal is a narrowband signal spanning one of a plurality offrequency bands. Each of the output matching components 560 a-560 ccorresponds to one of the plurality of frequency bands and is configuredto provide matching functionality at that frequency band. The outputmatching components 560 a-560 c can further include filteringfunctionality and be configured to filter the signal at the collector ofthe second transistor to the frequency band.

Thus, a band select signal (BSS) indicating the frequency band of theinput RF signal is provided to the band switch 571. In response, theband switch 571 routes the signal from the collector of the secondtransistor 551 (e.g., the output of the cascode power amplifier) to acorresponding output matching component 560 a-560 c. The band switch 571can be, for example, a single-pole/multi-throw (SPMT) switch. The outputof the corresponding output matching component is provided to theantenna 580 via the antenna switch 572. The antenna switch 572 can,similarly, be a SPMT switch controlled by the band select signal.Alternatively, the antenna switch 572 can be a combiner that outputs thesum of the inputs.

In various implementations, the band switch 571 is implemented using SOI(silicon-on-insulator) or PHEMT (psuedomorphic high-electron-mobilitytransistor) technology. This may require an additional semiconductor dieto support the function, adding size and cost to the solution. Thecascode power amplifier and the band switch 571 may be implemented on asingle SOI die. However, this may result in degraded RF performance forthe power amplification system 500. A BiHEMT (bipolar-high electronmobility transistor) process may be used that maintains the RFperformance of the power amplification system 500, but may increase thecost and complexity of the system. Further, these solutions mayintroduce loss into the system, such as insertion loss of the switch,degrading efficiency of the system and increasing the current drain onthe amplifier.

Described herein is an alternative solution using a cascode poweramplifier as the gain stage that switches between multiple common basecascode gain stages to support multiple frequency bands. This solutionutilizes a cascode amplifier stage and accomplishes the band selectionthrough switching of the active cascode stage. Given that the cascodesection may be present in the amplifier architecture in order to providehigh gain and improved ruggedness, the addition of additional parallelcascode stages may not introduce any loss (or any significant loss) intothe signal path. Thus, band switching may be accomplished withoutdegrading system efficiency. Selection of the desired band may beaccomplished through selective activation of individual bias paths or asingle bias path can be present which is directed to activate the biaspath of the desired band through band select logic.

Thus, in some implementations as described below, a multi-band poweramplifier can include multiple cascode base stages and not include aband switch. Such a solution may offer the advantage of sharing a commonRF gain path without adding the loss of a band switch where bandselection is also accomplished without additional process technologycomplexity or additional die, resulting in a highly integrated andlow-cost solution.

FIG. 6 shows that in some embodiments, a power amplification system 600can include a cascode configuration with multiple common base cascodestages. The power amplification system 600 includes a cascode poweramplifier including a common emitter stage and multiple parallel commonbase stages. The common emitter stage includes a first transistor 652having an emitter coupled to a ground potential. Each common base stageincludes a second transistor 651 a-651 c having a base coupled, via arespective capacitor 643 a-643 c, to the ground potential. The firsttransistor 652 includes a base coupled, via a capacitor 645 and an inputmatching component 630, to an RF input for receiving an input RF signal.The first transistor 652 also has a collector coupled to the emitter ofeach of the second transistors 651 a-651 c.

Each of the second transistors 651 a-651 c has a collector coupled, viaa respective inductor 641 a-641 c, to a supply voltage (Vcc). Thecollector of each of the second transistors 651 a-651 c is also coupled,via a respective output matching components 660 a-660 c and an antennaswitch 670, to an antenna 680 for transmitting an output RF signal. Inparticular, the respective collectors of the plurality of secondtransistors 651 a-651 c are coupled to the antenna switch 670 without anintervening band switch (e.g., the band switch 571 of FIG. 5).

The power amplification system 600 includes a biasing circuit forbiasing the first transistor 652 and one or more of the secondtransistors 651 a-651 c. The biasing circuit includes a common emitterbiasing component 620 that is coupled to the base of the firsttransistor 652 via an RC decoupling component. The RC decouplingcomponent includes a resistor 644 coupled between the common emitterbiasing component 620 and the base of the first transistor 652 andfurther includes a capacitor 645 coupled between the RF input and thebase of the first transistor 652.

The biasing circuit further includes a plurality of common base biasingcomponents 610 a-610 c, each one coupled to the base of a respectivesecond transistor 651 a-651 c via a respective RC decoupling component.Each RC decoupling component includes a resistor 642 a-642 c coupledbetween the common base biasing component 610 a-610 c and the base ofthe second transistor 651 a-651 c and further includes a capacitor 643a-643 c coupled between the ground potential and the base of the secondtransistor 651 a-651 c.

The common emitter biasing component 620 is configured to, when enabled,receive a current from a current source 622 powered a battery voltage(Vbatt) and provide a biasing signal to the first transistor 652. Thebiasing signal may be a biasing current (e.g., the current generated bythe current source 622) or a biasing voltage. Similarly, each of thecommon base biasing components 610 a-610 c is configured to, whenenabled, receive a current from a respective current source 612 a-612 cpowered by the battery voltage and provide a biasing signal to itsrespective second transistor 651 a-651 c. As with the common emitterstage, the biasing signal may be a biasing current (e.g., the currentgenerated by the current source 612 a-612 c) or a biasing voltage.

The power amplification system 600 is configured to receive an input RFsignal via the RF input and provide, as an output RF signal, anamplified version of the input RF signal via the antenna. Typically, theinput RF signal spans one of a plurality of frequency bands. Each of theoutput matching components 660 a-660 c corresponds to one of theplurality of frequency bands and is configured to provide matchingfunctionality at that frequency band. The output matching components 660a-660 c can further include filtering functionality and be configured tofilter the signal at the collector of the respective second transistor651 a-651 c to the frequency band.

To transmit an RF signal in a particular frequency band, the poweramplification system 600 may receive an input RF signal at the RF input(coupled to the input matching component 630). The power amplificationsystem 600 enables the common emitter biasing component 620 (e.g., byactivating the current source 622 and/or providing an enable signal tothe common emitter biasing component 620) and also enables the commonbase biasing component 610 a-610 c for that particular frequency band(e.g., by activating the respective current source 612 a-612 c and/orproviding an enable signal to the common base biasing component 610a-610 c for that particular frequency band). The enable signals (CB1,CB2, or CB3) can be provided by a controller 690 in response to a bandselect signal (BSS) indicating the particular frequency band. In someimplementations, the current sources 612 a-612 c and/or the commonemitter biasing components 610 a-610 c for other frequency bands may beinactive.

The input RF signal may be partially amplified by the common emitterstage resulting in an intermediate RF signal at the collector of thefirst transistor 652 and the emitters of the second transistors 651a-651 c. The intermediate RF signal is further amplified by the commonbase stage biased by the activated current source 612 a-612 c andcorresponding common base biasing component 610 a-610 c. The furtheramplified RF signal is output from the collector of the biased commonbase cascode stage through a corresponding output matching component 660a-660 c that matches and filters the output RF signal to the particularfrequency band. The filtered output signal is coupled by the antennaswitch 670 to the antenna 680 and transmitted in the particularfrequency band.

FIG. 7 shows that in some embodiments, the power amplification system600 of FIG. 6 may be modified by replacing the respective cascodecurrent sources 612 a-612 c and common base biasing components 610 a-610c with a single common base current source 712 and a single common basebiasing component 710 with band select logic.

The common base bias component 710 may receive current from the currentsource 712 and a band select signal (BSS) indicative of a frequency band(or selecting an output to a common base cascode stage corresponding tothe frequency band). The signal may be received on a corresponding inputfor the frequency band of a plurality of inputs (not shown) or may bereceived on a signal input (as shown), the signal itself indicatingwhich of the outputs is to be biased using the input current. Forexample, the signal may be one of a plurality of voltage valuescorresponding to various outputs of the cascode bias component.

Thus, the power amplification system 700 includes a cascode poweramplifier including a common emitter stage and multiple parallel commonbase stages. The common emitter stage includes a first transistor 752having an emitter coupled to a ground potential. Each common base stageincludes a second transistor 751 a-751 c having a base coupled, via arespective capacitor 743 a-743 c, to the ground potential. The firsttransistor 752 includes a base coupled, via a capacitor 745 and an inputmatching component 730, to an RF input for receiving an input RF signal.The first transistor 752 also has a collector coupled to the emitter ofeach of the second transistors 751 a-751 c.

Each of the second transistors 751 a-751 c has a collector coupled, viaa respective inductor 741 a-741 c, to a supply voltage (Vcc). Thecollector of each of the second transistors 751 a-751 c is also coupled,via a respective output matching components 760 a-760 c and an antennaswitch 770, to an antenna 780 for transmitting an output RF signal.

The power amplification system 700 includes a biasing circuit forbiasing the first transistor 752 and one or more of the secondtransistors 751 a-751 c. The biasing circuit includes a common emitterbiasing component 720 that is coupled to the base of the firsttransistor 752 via an RC decoupling component. The RC decouplingcomponent includes a resistor 744 coupled between the common emitterbiasing component 720 and the base of the first transistor 752 andfurther includes a capacitor 745 coupled between the RF input and thebase of the first transistor 752.

The biasing circuit further includes common base biasing components 710having a plurality of outputs, each one coupled to the base of arespective second transistor 751 a-751 c via a respective RC decouplingcomponent. Each RC decoupling component includes a resistor 742 a-742 ccoupled between the common base biasing component 710 a-710 c and thebase of the second transistor 751 a-751 c and further includes acapacitor 743 a-743 c coupled between the ground potential and the baseof the second transistor 751 a-751 c.

The common emitter biasing component 720 is configured to receive acurrent from a current source 722 powered a battery voltage (Vbatt) andprovide a biasing signal to the first transistor 752. The biasing signalmay be a biasing current (e.g., the current generated by the currentsource 722) or a biasing voltage. Similarly, the common base biasingcomponent 720 is configured to, when enabled, receive a current from acurrent source 712 powered by the battery voltage and provide a biasingsignal to a selected one or more second transistors 751 a-751 c. As withthe common emitter stage, the biasing signal may be a biasing current(e.g., the current generated by the current source 712) or a biasingvoltage.

The power amplification system 700 is configured to receive an input RFsignal via the RF input and provide, as an output RF signal, anamplified version of the input RF signal via the antenna. Typically, theinput RF signal spans one of a plurality of frequency bands. Each of theoutput matching components 760 a-760 c corresponds to one of theplurality of frequency bands and is configured to provide matchingfunctionality at that frequency band. The output matching components 760a-760 c can further include filtering functionality and be configured tofilter the signal at the collector of the respective second transistor751 a-751 c to the frequency band.

To transmit an RF signal in a particular frequency band, the poweramplification system 700 may receive an input RF signal at the RF input(coupled to the input matching component 730). The power amplificationsystem 700 enables the common emitter biasing component 720 (e.g., byactivating the current source 722 and/or providing an enable signal tothe common emitter biasing component 720) and also enables the commonbase biasing component 710 (e.g., by activating the current source 712and/or providing an enable signal to the common base biasing component710). The common base biasing component 710 can, in response to a bandselect signal indicating the particular frequency band, provide abiasing signal via a corresponding output and bias the correspondingsecond transistor 751 a-751 c.

FIG. 8 shows that in some embodiments, a power splitter 800 can includea cascode power amplifier with multiple common base stages. WhereasFIGS. 5-7 describe a power amplification system for producing an outputRF signal as an amplified version of an input RF signal, a similararchitecture can be used as a power splitter as shown in FIG. 8. Unlikea typical passive splitter, the power splitter 800 of FIG. 8 introducessignal gain (as a power amplification system) as opposed to a passivesplitter which typically introduces signal loss.

The power splitter 800 includes a cascode power amplifier including acommon emitter stage and multiple parallel common base stages. Thecommon emitter stage includes a first transistor 852 having an emittercoupled to a ground potential. Each common base stage includes a secondtransistor 851 a-851 b having a base coupled, via a respective capacitor843 a-843 c, to the ground potential. The first transistor 852 includesa base coupled, via a capacitor 845 and an input matching component 830,to an RF input for receiving an input RF signal. The first transistor852 also has a collector coupled to the emitter of each of the secondtransistors 851 a-851 b.

Each of the second transistors 851 a-851 b has a collector coupled, viaa respective inductor 841 a-841 b, to a supply voltage (Vcc). Thecollector of each of the second transistors 851 a-851 c provides arespective output RF signal.

The power splitter 800 includes a biasing circuit for biasing the firsttransistor 752 and one or both of the second transistors 851 a-851 b.The biasing circuit includes a common emitter biasing component 820 thatis coupled to the base of the first transistor 852 via an RC decouplingcomponent. The RC decoupling component includes a resistor 844 coupledbetween the common emitter biasing component 820 and the base of thefirst transistor 852 and further includes a capacitor 845 coupledbetween the RF input and the base of the first transistor 852.

The biasing circuit further includes common base biasing components 810having a plurality of outputs, each one coupled to the base of arespective second transistor 851 a-851 b via a respective RC decouplingcomponent. Each RC decoupling component includes a resistor 842 a-842 bcoupled between the common base biasing component 810 a-810 b and thebase of the second transistor 851 a-851 b and further includes acapacitor 843 a-843 b coupled between the ground potential and the baseof the second transistor 851 a-851 b.

The common emitter biasing component 820 is configured to receive acurrent from a current source 822 powered a battery voltage (Vbatt) orother voltage and provide a biasing signal to the first transistor 852.The biasing signal may be a biasing current (e.g., the current generatedby the current source 812) or a biasing voltage. Similarly, the commonbase biasing component 820 is configured to receive a current from acurrent source 812 powered by the battery voltage or other voltage andprovide a biasing signal to a selected one or more of the secondtransistors 851 a-851 b based on a received control signal. In someembodiments, the control signal is a band select signal (e.g., forimplementing a multi-band power amplification system).

When the control signal causes the common base bias component 810 tobias only one of the second transistors 851 a-851 b, an amplifiedversion of the input RF signal is output at a corresponding output ofthe power splitter (RFoutA or RFoutB). When the control signal causesthe common base bias component 810 to bias both of the secondtransistors 851 a-851 b, an amplified version of the input RF signal issplit and output at both outputs of the power splitter (RFoutA andRFoutB).

Although FIG. 8 includes two common base stages, it is to be appreciatedthat some implementations could include three or more stages to split aninput RF signal to three or more outputs. In some implementations, withthree or more outputs, the power splitter can, according to the controlsignal, split the input RF signal to more than one, but less than all,of the outputs.

FIG. 9 shows a flowchart representation of a method of amplifying an RFsignal. In some implementations (and as detailed below as an example),the method 900 is at least partially performed by a controller, such asthe controller 690 of FIG. 6. In some implementations, the method 900 isat least partially performed by processing logic, including hardware,firmware, software, or a combination thereof. In some implementations,the method 900 is at least partially performed by a processor executingcode stored in a non-transitory computer-readable medium (e.g., amemory).

The method 900 begins, at block 910, with the controller providing aninput RF signal with a particular frequency band to an RF input of acommon emitter cascode stage of a power amplification system.

At block 920, the controller selectively, based on the particularfrequency band, biases one (or more) of a plurality of parallel commonbase cascode stage of the power amplification system. The controller canbias the common base cascode by transmitting a band select signal to acommon base biasing component, by enabling a corresponding common basebiasing component, by enabling a corresponding current source, or byother methods.

At block 930, the controller transmits an amplified RF signal, theamplified RF signal being the input RF signal amplified by the poweramplification system. The controller can, in some implementations,transmit the amplified RF signal by indicating that signal is beingtransmitted. In some implementations, the controller transmits theamplified RF signal by coupling the amplified RF signal to an antenna.In some implementations, the amplified RF signal is transmitted by thepower amplification system without further action by the controller.

FIG. 10 shows that in some embodiments, some or all of poweramplification systems (e.g., those shown in FIGS. 5-7) can beimplemented, wholly or partially, in a module. Such a module can be, forexample, a front-end module (FEM). In the example of FIG. 10, a module300 can include a packaging substrate 302, and a number of componentscan be mounted on such a packaging substrate. For example, an FE-PMICcomponent 304, a power amplifier assembly 306, a match component 308,and a duplexer assembly 310 can be mounted and/or implemented on and/orwithin the packaging substrate 302. The power amplifier assembly 306 mayinclude a cascode system 307 such as those described above with respectto FIGS. 5-7. Other components such as a number of SMT devices 314 andan antenna switch module (ASM) 312 can also be mounted on the packagingsubstrate 302. Although all of the various components are depicted asbeing laid out on the packaging substrate 302, it will be understoodthat some component(s) can be implemented over other component(s).

In some implementations, a device and/or a circuit having one or morefeatures described herein can be included in an RF device such as awireless device. Such a device and/or a circuit can be implementeddirectly in the wireless device, in a modular form as described herein,or in some combination thereof. In some embodiments, such a wirelessdevice can include, for example, a cellular phone, a smart-phone, ahand-held wireless device with or without phone functionality, awireless tablet, etc.

FIG. 11 depicts an example wireless device 400 having one or moreadvantageous features described herein. In the context of a modulehaving one or more features as described herein, such a module can begenerally depicted by a dashed box 300, and can be implemented as, forexample, a front-end module (FEM).

Referring to FIG. 11, power amplifiers (PAs) 420 can receive theirrespective RF signals from a transceiver 410 that can be configured andoperated in known manners to generate RF signals to be amplified andtransmitted, and to process received signals. The transceiver 410 isshown to interact with a baseband sub-system 408 that is configured toprovide conversion between data and/or voice signals suitable for a userand RF signals suitable for the transceiver 410. The transceiver 410 canalso be in communication with a power management component 406 that isconfigured to manage power for the operation of the wireless device 400.Such power management can also control operations of the basebandsub-system 408 and the module 300.

The baseband sub-system 408 is shown to be connected to a user interface402 to facilitate various input and output of voice and/or data providedto and received from the user. The baseband sub-system 408 can also beconnected to a memory 404 that is configured to store data and/orinstructions to facilitate the operation of the wireless device, and/orto provide storage of information for the user.

In the example wireless device 400, outputs of the PAs 420 are shown tobe matched (via respective match circuits 422) and routed to theirrespective duplexers 424. In some embodiments, the power amplifiers 420and match circuits 422 can be at least part of the matching andfiltering components of FIGS. 5 and 6 and/or being included as part ofthe cascode system 307. Such amplified and filtered signals can berouted to an antenna 416 through an antenna switch 414 for transmission.In some embodiments, the duplexers 424 can allow transmit and receiveoperations to be performed simultaneously using a common antenna (e.g.,416). In FIG. 8, received signals are shown to be routed to “Rx” paths(not shown) that can include, for example, a low-noise amplifier (LNA).

A number of other wireless device configurations can utilize one or morefeatures described herein. For example, a wireless device does not needto be a multi-band device. In another example, a wireless device caninclude additional antennas such as diversity antenna, and additionalconnectivity features such as Wi-Fi, Bluetooth, and GPS.

As described herein, one or more features of the present disclosure canprovide a number of advantages when implemented in systems such as thoseinvolving the wireless device of FIG. 11. For example, the disclosedarchitecture may replace a PHEMT or SOI band switch with a cascodeswitching function within the PA core. Such a solution may offer theadvantage of sharing a common RF gain path without adding the loss of aband select where band selection is also accomplished without additionalprocess technology complexity or an additional die. Further, replacing apassive splitter with an active splitter replaces signal loss withsignal gain.

Unless the context clearly requires otherwise, throughout thedescription and the claims, the words “comprise,” “comprising,” and thelike are to be construed in an inclusive sense, as opposed to anexclusive or exhaustive sense; that is to say, in the sense of“including, but not limited to.” The word “coupled”, as generally usedherein, refers to two or more elements that may be either directlyconnected, or connected by way of one or more intermediate elements.Additionally, the words “herein,” “above,” “below,” and words of similarimport, when used in this application, shall refer to this applicationas a whole and not to any particular portions of this application. Wherethe context permits, words in the above Description using the singularor plural number may also include the plural or singular numberrespectively. The word “or” in reference to a list of two or more items,that word covers all of the following interpretations of the word: anyof the items in the list, all of the items in the list, and anycombination of the items in the list.

The above detailed description of embodiments of the invention is notintended to be exhaustive or to limit the invention to the precise formdisclosed above. While specific embodiments of, and examples for, theinvention are described above for illustrative purposes, variousequivalent modifications are possible within the scope of the invention,as those skilled in the relevant art will recognize. For example, whileprocesses or blocks are presented in a given order, alternativeembodiments may perform routines having steps, or employ systems havingblocks, in a different order, and some processes or blocks may bedeleted, moved, added, subdivided, combined, and/or modified. Each ofthese processes or blocks may be implemented in a variety of differentways. Also, while processes or blocks are at times shown as beingperformed in series, these processes or blocks may instead be performedin parallel, or may be performed at different times.

The teachings of the invention provided herein can be applied to othersystems, not necessarily the system described above. The elements andacts of the various embodiments described above can be combined toprovide further embodiments.

While some embodiments of the inventions have been described, theseembodiments have been presented by way of example only, and are notintended to limit the scope of the disclosure. Indeed, the novel methodsand systems described herein may be embodied in a variety of otherforms; furthermore, various omissions, substitutions and changes in theform of the methods and systems described herein may be made withoutdeparting from the spirit of the disclosure. The accompanying claims andtheir equivalents are intended to cover such forms or modifications aswould fall within the scope and spirit of the disclosure.

What is claimed is:
 1. A method for splitting an input radio-frequency(RF) signal, the method comprising: combining the input RF signal with acommon emitter biasing signal to bias a first transistor of a commonemitter stage of a cascode amplifier configuration; generating anintermediate RF signal at a collector of the common emitter stage;biasing simultaneously, using a common base biasing signal, two or moreof a plurality of parallel second transistors that form a common basestage of the cascode amplifier configuration, each second transistor ofthe plurality of parallel second transistors having a respective emittercoupled to the collector of the first transistor; and amplifying theintermediate RF signal using each of the two or more of the plurality ofparallel second transistors to generate two or more amplified RF signalsthat are output at respective output ports.
 2. The method of claim 1further comprising generating a control signal to indicate which of theplurality of parallel second transistors to simultaneously bias.
 3. Themethod of claim 1 further comprising providing a supply voltage to eachcollector of the plurality of parallel second transistors.
 4. The methodof claim 1 further comprising simultaneously biasing three or more ofthe plurality of parallel second transistors.
 5. The method of claim 1further comprising providing a battery voltage to bias the firsttransistor and to simultaneously bias the two or more of the pluralityof parallel second transistors.
 6. The method of claim 1 furthercomprising impedance matching the input RF signal prior to combining theinput RF signal with the common emitter biasing signal.